This invention relates to novel solid solutions of copper phthalocyanine compounds, processes for their synthesis, and their use for pigmentation of, for example, fibers, plastics, coatings, and printing inks. In particular, this invention relates to compositions in which tetrachloro copper phthalocyanine and C.I. Pigment Green 7 are mixed under certain conditions with each other to form solid solutions that are quite different from both physical mixtures of such compounds and from the individual compounds themselves.
The term "solid solution" as used herein describes a well recognized physical property of certain solid substances. In a solid solution, the molecules of the components enter into the same crystal lattice, usually (but not always) the crystal lattice characteristic of one of the components. The X-ray pattern of the resulting crystalline solid is characteristic and can be clearly differentiated from the pattern of a physical mixture of the same components in the same proportion. Thus, the X-ray peaks of each component of a physical mixture can be distinguished, whereas a characteristic of a solid solution is the disappearance and shift of many of these peaks.
Solid solutions of other types of pigments have been reported to provide advantageous color properties. For example, U.S. Pat. No. 3,160,510 discloses solid solutions of certain quinacridone pigments having improved tinctorial and lightfastness properties. Suitable methods for preparing solid solutions of quinacridone pigments are described, for example, in U.S. Pat. Nos. 3,160,510, 3,298,847, 3,607,336, and 4,895,949.
Three important properties of the present invention make the new products particularly useful as pigments. First, in contrast to simple physical mixtures wherein the color is usually a direct function of the additive effects of the two components, the new solid solution of the present invention show unexpected and advantageous coloristic properties.
A second valuable property of the invention is an enhancement of lightfastness, which frequently accompanies the formation of solid solution. In physical mixtures of two pigments, the components show their individual behaviors upon exposure to light, often resulting in marked changes of hue as one pigment component fades more than the other. In contrast, however, the solid solutions of the present invention appear to behave as a single substance with respect to hue stability.
Third, the present invention makes it possible to prepare pigments not readily available as single compounds. For example, C.I. Pigment Green 37, described in the Colour Index as a turquoise pigment, is also known as "octochloro copper phthalocyanine," and thus has a chlorine content within the broad range described for solid solutions according to the invention. Octochloro copper phthalocyanine can be prepared by condensing dichlorophthalic anhydride, a difficult to obtain and expensive material. This pigment can also be prepared by direct chlorination of copper phthalocyanine, but the preparative method is expensive and difficult to control. See K. Venkataraman, The Chemistry of Synthetic Dyes, Vol. II (New York: Academic Press, 1952), pages 1132, 1133); N. M. Bigelow and M. A. Perkins, "Phthalocyanine Pigments," in The Chemistry of Synthetic Dyes and Pigments, ed. H. A. Lubs (Malabar, Florida: Robert E. Krieger Publishing Company, 1955), pages 598-599. Octochloro copper phthalocyanine does not, however, exhibit the advantageous properties observed for the solid solutions of the present invention.
The novel phthalocyanine pigment solid solutions of the present invention, when compared with the corresponding physical mixtures, as well as with the single-compound octochloro copper phthalocyanine mentioned above, give economically superior pigments and exhibit advantageous brilliancy, lightfastness, and tinctorial values.